Proper Thermistor Calibrations

When dealing with thermistors, sometimes it is important to calibrate the unit for optimal usage. This is as a result of certain applications needing tight accuracy requirements. A good deal of math goes into calibrating your unit properly, and so it is usually best to deal with trained professionals. Calibration works with the help of interpolation equations. These equations are used to set ranges at multiple temperatures. The correct equations need to be picked as well as the control temperatures being used. It is important to point out that beta tolerance and resistance tolerance have no effect on proper calibrations.

Different thermistors exist, and so calibration is not done the same way for all products. Calibrations are broken down into different schedules. The schedules allow people to know how to best calibrate their products. There are five main calibration schedules, but some of them are broken down into subgroups.

Schedule 1- This type of calibration is only used for certain types of thermistors (thermistor standards and ultra stable thermistor probes). With the help of a consistent temperature bath, integrating blocks are submerges in order to calibrate the thermistor.

Schedule 2- This type of calibration is used for all types of glass probe thermistors. Before getting calibrated with this schedule, all stability requirements related to temperature and time must be found and verified. A bath and block are used for this method as well. The main difference is how the SPRT is found.

Schedule 3- It is important that stability requirements are verified before calibration can begin. This schedule is for glass-enclosed beads and probes.

Schedule 4- This schedule are rather similar too 3, and so they get lumped together at times. This schedule will work for all thermistors. For this, resistance is measures with a Wheatstone bridge or a digital meter. In certain cases a data acquisition system can be use instead.

Schedule 5- This is also available for all thermistors. For this, a digital meter is used to help calibrate.

If you do not know what you are doing and do not have the right tools then your calibration work can be in vein. In order to get the most from your thermistors they must be calibrated to your specific time and temperature requirements. Ask a local thermistor company for help picking the proper schedule and going through the process of calibration.

Related Reading

Thermistors